main/python3: build --with-system-libmpdec (!18121) · Merge requests · alpine / aports

Debian, Ubuntu, Arch Linux etc. have used --with-system-libmpdec for a long time, so I suggest using it in Alpine, too.

There are no incompatibilities between mpdecimal-2.5.1 and _decimal.c in Python 3.8 except for the trivial build patch.

This PR depends on !18120 (merged) .

main/python3: build --with-system-libmpdec